Does a divorce befall the wife if the husband made divorce contingent upon her wearing the hijab, and she wore a headscarf (tarḥah) instead, then replaced it with a hijab before reaching the wedding venue, knowing that his intention was merely to compel her?

If the wife attends the wedding while wearing the hijab, then the oath is not broken, and the divorce conditioned on her attending the wedding without hijab is not triggered. This is unless the intention behind the oath was that she should wear the hijab in all her affairs, in which case the oath would be broken, and divorce would be triggered according to the majority of scholars, or an expiation for breaking an oath according to Sheikh Al-Islam Ibn Taymiyyah. It appears that no breach occurred, so neither divorce nor an expiation for an oath is required. Caution must be exercised when using such words to avoid jeopardizing the marriage.